Current amplifying system



Patented Dec. 4, 1934 UNITED STATES CURRENT AMIPLIFYING SYSTEM Julius Gourgues Aceves, New York, N. Y., assignor, by mesne assignments, to Radio Corporation of America, New York, N. 1., a corporation of Delaware Application August 13, 1924, Serial No. 731,818 Renewed April 12, 1934 13 Claims.

This invention relates to systems for amplifying electric currents by the use of vacuum or thermionic tubes, and particularly to such systems which may be advantageously used in radio telephone and telegraph receiving sets. Various attempts have been made to eliminate batteries in the operation of systems using such tubes, by the substitution for the batteries of current from commercial lighting systems of both the direct and alternating current type. These devices have not been entirely satisfactory, since complicated or heavy transformers and a large number of rectifying devices have been required, and the circuits were relatively involved and complicated. Furthermore, receiving sets with these systems using such current have heretofore been objectionable by reason of noises coining in with or caused by the currentfrom the commercial power and lighting systems.

An object of this invention is to provide an improved system for amplifying electric currents which will operate successfully; practically, and without noise from either a direct or alternating current commercial power supply; with which all batteries may be eliminated and at the same time the proper grid voltages or bias obtained for the most efficient and satisfactory operation of the tubes; and which will be relatively simple, compact and inexpensive. A further object is to provide an improved system of this type with which any desired and variable plate voltages may be impressed upon the plates of the tubes so that resistance or choke coil coupling for audio frequency amplification becomes a practical possibility. Other objects and advantages will be apparent from the following description of an embodiment of the invention and the novel features will be particularly pointed out hereinafter in claims.

In the accompanying drawing, I have illus* trated diagrammatically the circuit of a system operating in accordance with this invention.

Referring to the drawing, the system, as illustrated, is incorporated into a radio telephone and telegraph receiving apparatus utilizing one stage of radio frequency amplification, a detector and two stages of audio frequency amplification. The antenna 1 is connected to ground through the primary 2 of an inductance transformer 3 and a wire 4. The secondary winding 5 of the transformer 3 is connected into the grid circuit of the vacuum tube 6. The other vacuum tubes '7, 8 and 9 are coupled to one another and to the tube 6 in cascade, by any usual coupling means such as inductance, choke coil, or resistance coupling as will be explained more fully hereinafter. The filaments of the tubes are connected in series with one another by wires 10, 11 and 12, the filament of the tube 6 being connected by a wire 13 to ground through corresponding ends of the primary and secondary inductances 2 and 5 and the common ground lead 4.

The filament of the other end tube 9 is connected by a wire 14 to a plurality of resistances 15,

16 and 1'7, which are connected in series with one another and to the wire 14, the other end of the series connected resistances being connected by a wire 18 to a fuse 19 for connection therethrough to the positive lead from a source of direct current. The ground lead 4 is also connected to a fuse 20, which is also connected to a negative lead from a source of direct current, as will be explained more fully hereinafter.

The plate of the tube 6 is connected through the primary of a radio frequency transformer 21 and a wire 22 to the wire 18 connecting the resistances to the positive lead from the source of direct current. A positive voltage will thus be impressed upon the plate of the tube 6. The secondary of the transformer 21 is connected at one end through a grid leak and condenser device 23 to the grid of the detector tube '7, and at the other end to the grid return wire 24 through the plus side of the filament of that tube '7, so that a positive potential bias will normally be impressed upon the grid. The plate of the detector tube '7 is connected through the primary of an audio frequency transformer 25 and a wire 26 to the connection between the first and second resistances 15 and 16, so that a positive current will flow through the plate of the detector tube.

The secondary of the transformer,25 is connected at one end to the tube 8, forming a part of the first stage of audio frequency amplification, and at its other end is connected by a wire 2'7 to the negative terminal of the filament of the preceding tube '7, so that the potential bias on the grid of the tube 8 will be negative and in value equal to the fall of potential over the filaments of two tubes. The plate of the tube 8 is connected through an impedance 28 and a wire 29 to the connection between the resistances 16 and 17, so that a positive potential from the resistances will be impressed upon the plate of the tube 8.

The plate of the tube 8 is also connected by a wire 30 to the grid of the next tube 9 and includes therein between the grid and the connection to the impedance 28 a suitable condenser 31, as usual in resistance couplings between tubes. A high 110 resistance leak 32 is connected by a wire 33 between the grid of the tube 9 and the negative filament terminal of the preceding tube 8, so that a negative bias will be impressed upon the grid corresponding approximately in amount to the fall of potential across two filaments. The leak 32 is provided as usual in resistance couplings. The plate of the tube 9 is connected through a wire 34 to a suitable jack 35 for the phones or loud speaker, and the latter through a wire 36 is connected to the wire 22, so that a positive potential corresponding substantially to the potential impressed upon the wire 18 will be impressed upon the plate of the tube 9.

The wire 13 which forms a part of both the filament circuit and the grid return of the first tube 6 may have included therein a resistance 37 for producing upon the grid of that tube a negative bias depending upon the value of the resistance 37. The fuses 19 and may be directly connected to any commercial source of direct current, but in the negative lead from the source of direct current a suitable filter or reactor 38 must always be provided so as to eliminate the very strong noises that arise through the continuous disturbances of a very steep wave front in the commercial current circuit.

As illustrated, the source of direct current is a rectified current obtained from a commercial alternating current supply circuit. A transformer 39 is connected to the line circuit of the alternating current system, and the ends of the secondary of this transformer are connected to rectifying tubes 40, and the tubes 40 are also connected together and by a wire 41 to the fuse 19 so as to supply a positive potential current to the fuse 19. A conductor 42 'is connected to the middle point of the double secondary winding of the transformer, and through the filter or reactor 38 to the negative lead fuse 20.

One or more filters or reactors 43 may be connected in series in the wire 41 which supplies a positive current to the amplifying system, and

one or more condensers 44 of large capacity may be connected across between the wires '41 and 42 as usual in prior systems of rectifying current.

The rectifying devices 40 may be any of the usual rectifying devices but I have found that the commercially kno'n S tube rectifiers are very satisfa'ctory'for this purpose. It will be understood, however, that any othertype of rectifier may be utilized, and that where filament tubes are adopted, suitable circuit connections are made to the filaments to light the same.

The resistances 15, 16 and 17 may be of any suitable construction, but I have found that Mazda lamps of about 40 watts each are very inexpensive, convenient and satisfactory resistance units. The filters or reactors 43 may comprise inductances of value ranging from 2 to henrys and the condensers 44 may have capacities of sev eral micro farads, so that they will reduce the fluctuations or pulsations in the rectified current to such a small value that they will not cause an audible sound in the phones or loud speaker connected to jack 35. In any event, such sounds would be very faint, if audible at all, and would be very small in comparison with other disturbances foreign to the power supply system such as static and interferences.

In the operation of such a system as has just been described, the transformer 39 is connected to the alternating current supply line and the current therefromis transformed, preferably into a her voltage in the two secondary windings.

This transformer current of higher voltage is then rectified in the rectifiers and passes to the set through the fuses 19 and 20. The current will pass from the fuse 19 through the resistances 15, 16 and 17, the wire 14, the filaments of tube 9, the wire 12, the filament of tube 8, the wire 11, the filament of tube 7, the wire 10, the filament of tube 6, the wires 13 and 4 to'the fuse 20 in the negative supply lead. With all of the filaments connected'in series they will all be lighted, and the voltage upon the filaments will be determined by the voltage of the rectified current and the value of the resistances 15, 16 and 1'7. The resistances 15, 16 and 17 will be such that the voltage fall across the filaments will be that which the tubes are supposed to carry for their normal operation.

The drop of potential across the resistances 15, 16 and 17 is utilized to furnish the so-called B voltage for the plate circuits of the tubes. The maximum voltage fall across the resistances 15, 16 and 17 will be that between the wires 14 and 18 so that the wires 22 and 36, which are connected to the wire 18 and the plates of the first and last tubes will impress upon the plates of those tubes, the maximum voltage fall across the resistances. Since there is a slight voltage fall through the filaments, the potential over the plate of the first tube 6 will be slightly greater than that for the last tube 9 since the effective resistance determining the voltage fall or potential impressed upon the plate of any tube, will be measured by the resistance in the filament circuit between the wire 18 and the filament of that tube in question.

The plate circuit of the detector tube 7 is connected between the resistances l5 and 16 so that it will have impressed thereon a voltage corresponding to the fall in potential from the resistance 16 to the filament of the detector tube. The voltage impressed upon jthe plate of the tube 8 will be equal to the voltage fall from the resistance 17 to the filament of that tube. It will be observed that any desired plate voltage for any tube may be obtained by merely varying the points of connection of the plate circuit wires to the resistances l5, l6 and 17, but the arrangement shown is such as to give the plate voltages upon the various tubes, which are most commonly utilized in radio telephone and receiving sets.

. Obviously the wires 22, 26 and 29 may be connected at various other points in the filament circuits so as to obtain the desired plate voltages.

By connecting the grid return of the various tubes to different points in the filament circuit the desired grid bias, either positive or negative, may be obtained of such value as desired, depending upon the point in the filament circuit where the grid return is connected. In connection with the tube 6, the grid return is con-v nected to the filament through the resistance 37, which, for example, may be approximately 5 to 10 ohms, so that there will be a greater voltage fall between the filament and the grid return, thus causing a greater negative bias to be impressed upon the grid of the tube 6. Obviously a resistance similar to 37 may be included in the filament circuit between any of the tubes in order to enable one to vary the grid bias upon any of the other tubes in a similar manner.

The grid return of the detector tube is connected to the positive filament terminal of that tube, so that a positive bias will be impressed upon the grid as usual in radio telephone circuits. If a greater positive bias were desired, a resistance similar to 37 could be included in the filament circuit between the point of connection of the grid return to the filament circuit and the filament of the detector tube, or the grid return 24 could be connected to the positive filament terminal of one of the tubes 8 or 9 to increase the positive bias of the grid.

The grid return 27 of the tube 8 could be connected directly to the negative terminal of that tube where low plate voltages are employed, but where a greater negative bias on the grid is desired, the grid return may, as shown, be connected to the negative filament terminal of the tube 6 or 7, depending upon the degree of negative bias desired. A similar manner of obtaining a grid bias for the grid of tube 9 is illustrated in connection with the resistance coupling between the tubes.

It will be observed that with this system, the use of A, B and C batteries is entirely unnecessary, and all of the direct current necessary for the operation of the system is obtained from a commercial supply of either direct or alternating current. It will be observed that with this arrangement the desired extent of grid bias may be obtained in a simple manner without the use of 0" batteries, and any value of plate current may be obtained for any of the tubes independently of the plate voltage impressed upon any of the other tubes of the system.

While both inductance and resistance couplings have been illustrated in the same system in order to illustrate to some extent the possibilities and scope of the system, it will be understood that any or all of the couplings may be inductance, choke coils, or resistance couplings as usually employed heretofore in sets, or as may be desired. Where the current is obtained from a source of alternating current, the voltage of the rectified current may be of any value desired by stepping up the voltage of the current obtained from the transformer. For example, the voltage of the rectified current, and the resistances 15, 16 and 17, may be selected of such values as to provide for the impressing upon the plates circuits of the tubes of voltages as high as 300 or 400 volts, so that resistance coupling for audio frequency amplification becomes a practical possibility. This is particularly valuable, since it is well recognized that with resistance coupling for audio frequency amplification, un-

paralleled quality of speech and music may be obtained from a radio receiving set utilizing this Another feature of the invention is the connection oi the filaments in series, since by this method only two ordinary s-type tube rectifiers are necessary to supply all of the current desired, whereas, if the filaments are not in series, it might be necessary to use two a tube rectifiers for every vacuum tube of the receiving set, and

is, therefore, exceptionally economical of line current. and the apparatus required is reduced to a minimum.

It will be obvious that various changes in the details and ts of parts and connections, which have been herein described and illustrated in order to explain the nature of the invention, may be made by those skilled in the art within the principle and scope of the invention as in the appended claims.

I claim:

1. In a vacuum tube system for amplifying electric currents, a plurality of vacuum tubes coupled in cascade, the filaments of said tubes being connected in series with one another, a single source of direct current for said entire system connected to the series connected filaments to heat the same, the grid return of each tube being connected to such a point in the circult of the series connected filaments as will produce the desired bias on the grid, resistance means included in series with said connected filaments and said source of current for impressing the proper voltage across the filaments, and means for utilizing the voltage drop across said series connected resistance means for supplying plate current to said tubes.

2. In a vacuum tube system for amplifying electric currents, a plurality of vacuum tubes coupled in cascade, the filaments of said tubes being connected in series with one another, a single source of direct current for said entire system connected to said series connected filaments to light the same, resistance means included in series with the source of current and the, filaments to place the proper voltage across the filaments, and current supply connections from the plate circuits of the tubes to different points in the filament circuit whereby the plate circuits will have impressed thereon voltages corresponding to the potential drop from said different points to the tube filaments.

3. In a vacuum tube system for amplifying electric currents, a plurality of vacuum tubes coupled in cascade, the filaments of said tubes being connected in series with one another, a source of alternating current, a single rectifier connected thereto, a resistance connected in series with said filaments, said filaments and resistance all being connected in series and across the output terminals of said rectifier, connections from said grids to circuit pointsbeyond the filament of an adjacent vacuum tube for producing a negative bias thereon, connections from the plates of certain of said vacuum tubes to said resistance for the impressing of maximum voltage upon certain oi said vacuum tubes, and connections from intermediate points on said resistance to the plates of other of said vacuum tubes for the impressing of lower voltages thereon.

4. In a vacuum tube system, in combination, a plurality of cascade triode vacuum tubes, a single alternating current source of power for the energization thereof, a single rectifier device for converting power from said source into direct current for supplying the entire system with the necessary current at proper potentials, a filter for smoothing said direct current, and means for utilizing said direct current for the simultaneous heating of the filaments of said tubes, produc-' tion of voltage bias for the grids of said tubes, and production of high potential plate current for said tubes.

5. Radio receiving apparatus comprising in combination a plurality of electron tubes, one of said tubes being arranged to function as a detector and others of said tubes being arranged to operate as amplifiers, cathodes, anodes, and grid electrodes for said tubes, power supply means for said electron tubes, a power distribution circuit connected across said power supply means, means for obtaining uni-directional current from said power supply means independently of the character of said power supply means and connections between said cathodes and anodes with points in said power distribution circuit for deriving operating potential for said electron tubes.

6. Radio receiving apparatus comprising in combination a plurality of electron tubes each having a cathode, an anode, and a grid, an input circuit ior each of said tubes including the cathode and grid of each tube, an output circuit for each tube including the anode and cathode thereof, with the output circuit of one of said tubes interlinked with the input circuit of a succeeding tube, a power supply system for said electron tubes, means for obtaining uni-directional current from said power supply system, connections with said means including a power distribution circuit constituted in part by said cathodes, and connections from points in said power distribution circuit to each of said anodes and grids for operating said tubes at a proper working potential, said circuits operating from direct as well as an alternating current source.

'7. In a radio receiving apparatus for universal operation on direct as well as alternating current power supply the combination of a plurality of electron tubes each having a cathode, an anode, and a grid, of a series circuit including said cathodes and a resistance, a power supply circuit adapted to be connected to a source of alternating as well as direct current for supplying uni-directional current to said series circuit, means interposed between said power supply circuit and said series circuit for smoothing out the uni-directional current delivered to said series circuit, and means connected to various points along said resistance for deriving direct current potential for each of said anodes and grids, whereby said electron tubes may be operated at a proper point on the characteristic curves thereof independently of the character of said power supply.

8. In a radio receiving apparatus, the combination of a plurality of electron tubes, each having a cathode, anode and grid, a series circuit including said cathodes, and a resistance, a source of alternating as well as direct current, means for obtaining smooth uni-directional current and applying that current across said series circuit, and connections from said anodes to points along said resistance and connections from grid returns to points along the series of cathodes, whereby difierent potentials can be applied to said anodes and grids for operating said tubes at the proper points on the characteristic curves thereof independently of the character of said source.

9. A radio receiving apparatus arranged to operate universally from a direct as well as an alternating current power supply comprising an electron tube amplification system, anode and cathode circuits for said electron tube amplification system, and a power supply system having input and output circuits with the output circuit thereof connected with said anode and cathode circuits and the input circuit thereof connected to said power supply for supplying uni-directional current to said anode and cathode circuits.

10. In a vacuum tube system for amplifying electric currents, a plurality of vacuum tubes coupled in cascade, and having filaments connected in series with one another, a single sourceof current for said entire system connected to the series connected filaments to heat the same, connections for biasing the grids of the tubes from a circuit connected to said source of current, resistance means included in series with said connected filaments and said source of current for impressing the proper voltage across the filaments, and means for utilizing the voltage developed across said source of current for supplying plate potential to said tubes.

11. In a vacuum tube system for electric curments, a plurality of vacuum tubes coupled in cascade, and having filaments connected in series with one another, a single source of current for said entire system, a circuit connecting said filaments in series, resistance means included in series with the source of current and the filaments to place the proper voltage across the filaments, and circuit connections for utilizing desired proportions of the potential developed across said single source of current to bias the grids and to supply plate potential to said tubes.

12. In radio receiving apparatus for universal operation on direct as well as alternating current power supply the combination of a plurality of electron tubes each having a cathode, an anode, and a grid, a series circuit for heating said cathodes, a resistance in series in said circuit, a power supply circuit adapted to be connected to a source of alternating as well as direct current for supplying uni-directional current for said apparatus, filter means for smoothing out the uni-directional current delivered to said apparatus, and means connected to obtain direct potential for each of said anodes and grids from the uni-directional current from said filter means, whereby said electron tubes may be operated at a proper point on the characteristic curves thereof independently of the character of said power upply.

13. In a vacuum tube system, in combination, a plurality of cascade connected vacuum tubes, each including an anode, a cathode and a grid, a single source of power for the energization thereof, a rectifier device 'for converting alternating current from said source into direct current for supplying grid bias and anode potentials to the system, a filter for smoothing said direct current, and a series circuit for heating said cathodes from said source of power.

JULIUS GOURGUES ACEVES. 

